createNewUserButton.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {

                //Pattern para validar el email
                Pattern pattern1 = Pattern.compile("(?:[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\\.[a-z0-9!#$%" +
                "&'*+/=?^_`{|}~-]+)*|\"(?:[\\x01-\\x08\\x0b\\x0c\\x0e-\\x1f\\x21\\x23-\\x5b\\x5d-\\x" +
                "7f]|\\\\[\\x01-\\x09\\x0b\\x0c\\x0e-\\x7f])*\")@(?:(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9]" +
                ")?\\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?|\\[(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]" +
                "?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?|[a-z0-9-]*[a-z0-9]:(?:[\\x01-\\x08" +
                "\\x0b\\x0c\\x0e-\\x1f\\x21-\\x5a\\x53-\\x7f]|\\\\[\\x01-\\x09\\x0b\\x0c\\x0e-\\x7f])+)\\])");

                //Pattern para validar el nick y el contraseña
                Pattern pattern2 = Pattern.compile("^.[^ ]{4,20}$");

                //Recogida de email, nick y contraseña
                Matcher matcherEmail = pattern1.matcher(newEmail.getText().toString());
                Matcher matcherNick = pattern2.matcher(newNick.getText().toString());
                Matcher matcherPassword = pattern2.matcher(newPassword.getText().toString());

                //Validación
                if (matcherEmail.find()
                & matcherNick.find()
                & matcherPassword.find()
                & newPassword.getText().toString().equals(repeatNewPassword.getText().toString())){

                    serviceExecution("http://192.168.1.68:8080/buksu/insertUsers.php");

                } else if (!matcherEmail.find()) {

                    Toast.makeText(getApplicationContext(), "La dirección de correo electrónico no es correcta.", Toast.LENGTH_SHORT).show();
                    newEmail.getText().clear();

                } else if (!matcherNick.find()) {

                    Toast.makeText(getApplicationContext(), "El nick tiene que tener entre 5 y 20 caracteres y ningún espacio.", Toast.LENGTH_SHORT).show();
                    newNick.getText().clear();

                } else if (!matcherPassword.find()) {

                    Toast.makeText(getApplicationContext(), "La contraseña tiene que tener entre 5 y 20 caracteres y ningún espacio.", Toast.LENGTH_SHORT).show();
                    newPassword.getText().clear();
                    repeatNewPassword.getText().clear();

                } else {

                    Toast.makeText(getApplicationContext(), "Las contraseñas deben coincidir.", Toast.LENGTH_SHORT).show();
                    newPassword.getText().clear();
                    repeatNewPassword.getText().clear();

                }

            }
        });